Wikipedia:Reference desk/Archives/Computing/2010 August 23

= August 23 =

Installation & Setup of XRDP/rdesktop
Hi. I have a thin client in one city and a virtual-machine hosted on a server located somewhere else. I'm trying to use the thin client to access the virtual-machine over the Internet via Remote Desktop Protocol. I am providing the intended specifications of both the thin client and the virtual-machine below.

Micro-Star International MS-9A19 (Thin Client):  Intel Atom N270 1.6GHz Processor 2GB 667MHz SO-DIMM Hitachi TravelStar 7K320 80GB 2.5" 7200rpm SATA II HDD (HTS723280L9A360) Ubuntu 10.04 Netbook Edition (32-bit Version) Note: The monitor, keyboard and mouse are not listed, but would be attached to the thin client.  Virtual Machine:  four Virtual Processors 32GB RAM Allocation</li> <li>800GB VHD Allocation</li> <li>Debian 5.0.4 Linux (64-bit Version)</li> </ul> The basic idea here is to install XRDP on the Virtual Machine, and rdesktop on the thin client, and then remotely access and control the Virtual Machine from the thin client. I have downloaded both XRDP and rdesktop, but they both consist each of an archive containing many folders, sub-folders and files; but none of the files in either are executable(s), and neither do any of the other files seem to be capable of executing an installation. So how do I actually install and setup rdesktop on the thin client and XRDP on the virtual machine? Rocketshiporion Monday 23-August-2010, 12:34am GMT  —Preceding undated comment added 00:34, 23 August 2010 (UTC).


 * Both XRDP and rdesktop are in the Ubuntu repositories, so <tt>sudo apt-get install XRDP</tt> and <tt>sudo apt-get install rdesktop</tt> as appropriate. -- Finlay McWalter ☻ Talk 10:43, 23 August 2010 (UTC)


 * And it should be the same for the plain Debian ones. -- Finlay McWalter ☻ Talk 11:48, 23 August 2010 (UTC)


 * Out of curiosity, is there a particular reason why you chose XRDP over the other available methods of remotely accessing a Linux host? Say, NoMachine/FreeNX, X2go, VNC, or just plain ssh with X-forwarding enabled? -- 78.43.71.155 (talk) 16:31, 23 August 2010 (UTC)


 * Better yet, plain ssh. Assuming these are VMs intended for running servers, you'd typically put a headless server distribution on them and remotely administer them over ssh. GUI sysadmin tools on Linux are, generally, pretty much second-class citizens when compared to just editing the relevant config files; and the text interface is an order of magnitude easier to script and automate than trying to automate the GUI. -- Finlay McWalter ☻ Talk 17:46, 23 August 2010 (UTC)


 * Obviously, that depends on the VM host software you choose. For example, VMware Server has a web-based GUI where ssh+portforwarding will work nicely, while it is quite annoying to administer it with shell commands (I ended up writing a dialog-based menu for the tasks I need most.) -- 78.43.71.155 (talk) 19:56, 23 August 2010 (UTC)


 * These VMs are intended to run client desktops, and a GUI is a requirement. As for the remote access protocol, I have been a Microsoft Windows user thus far, and so I'm only familiar with Microsoft's Remote Desktop Protocol, which is the protocol used by XRDP and rdesktop. And I would like to stick with a protocol which allows the flexibilty for both Windows and Linux machines to remote into a Linux VM. By the way, the hypervisor to be used here is the Hyper-V function of Microsoft Windows Server 2008 R2 Enterprise Edition. Rocketshiporion

How do you call the paint function at any point in the code
Consider this following Applet code: Pressing the button "a" should display the number 1, but instead it displays the number 2. This would suggest that the repaint function is being called at the end of actionPerformed rather than at the point where it appears to be called in the program. Is there any way to call the paint function in the middle of actionPerformed rather than at the end?--115.178.29.142 (talk) 01:56, 23 August 2010 (UTC)


 * Strictly, in the code above, paint isn't just called after actionPerformed, it's called asynchronously in another thread. That's the way things are supposed to be, and mostly that should work fine for you. If you really must call paint right there in the button's event handler, call the applet's getGraphics method, which returns a Graphics object that you can then pass to the paint method. Note that this works okay as long as you're just using AWT for the GUI; if you use Swing, which isn't reentrant, things get more complex.  Incidentally you may find things work more efficiently if you store the result of that getFont method in a member variable of PaintTest, so that you don't have to keep reconstructing it every paint. -- Finlay McWalter ☻ Talk 09:09, 23 August 2010 (UTC)
 * The problem with paint(getGraphics) is that what is already displayed in the applet doesn't get removed. For instance, if you replace repaint with paint(getGraphics) in the above code and then you press the button "a" you get a 1 superimposed over the 0 that was there originally.--115.178.29.142 (talk) 22:20, 23 August 2010 (UTC)
 * That's a problem with your code. As the code responsible for repainting a control, that code is responsible for painting its background too. -- Finlay McWalter ☻ Talk 22:27, 23 August 2010 (UTC)
 * How do you paint the background then?--115.178.29.142 (talk) 00:06, 24 August 2010 (UTC)
 * You need to call clearRect(0,0,w,h) where w,h come from getSize. This is done automatically for you in the default implementation of java.awt.Component.update, which would be called if you used repaint dispatching. -- Finlay McWalter ☻ Talk 00:32, 24 August 2010 (UTC)
 * You may call <tt>repaint</tt> on a component at any time. This sends a message to the Paint thread, and "causes a call to this component's <tt>paint</tt> method as soon as possible"  (emphasis added).  Repaint is non-blocking - which means that the next line (i=2) gets executed immediately (though in reality, because this is a multithreaded system, this is a race condition with indeterminate behavior that can vary at runtime).  Painting gets called "as soon as possible" - which usually means "the next frame" - but this depends entirely on how busy the CPU and the graphics thread is; whether you have double-buffering; and so on.  When programming Java graphics, you need to be aware that the rendering is event driven, and not real-time - because all graphic rendering tasks are handled asynchronously through a separate thread.  This architecture is by design - it is intended to make your life easier as a graphics programmer.  If you have need for real-time requirements, you must implement your own graphics utilities - for example, servicing VSYNC interrupts - (this can be done in Java, with great difficulty); or use a different language that supports lower-level graphics access.  Or, if you choose to eliminate the race-condition and wait for the next paint event, you can use thread synchronization to guarantee the order that your Swing graphics and your program logic will execute.  Nimur (talk) 16:25, 23 August 2010 (UTC)

MacOS: num keys gone dead
I recently changed my keyboard setting from US to US-Extended, and probably did some other fiddling at the same time. Now my num keys (on the right) don't work, and tapping Num Lock only provokes an error beep. (Switching back to standard US doesn't help.) What did I do? —Tamfang (talk) 02:35, 23 August 2010 (UTC)


 * Which mac OS, what kind of keyboard, what kid of computer? -- Ludwigs 2  04:41, 23 August 2010 (UTC)

10.5.8; Adesso split keyboard (resembles MS Natural but with Apple keys); Mac Mini PPC. —Tamfang (talk) 06:36, 24 August 2010 (UTC)


 * I don't have a 10.5.x install to test on. though if I remember correctly, 10.5 when past 10.5.8 - have you not installed all the possible updates for some reason?  doing updates may resolve the problem.


 * you could also try this technique, which is a bit ham-handed but often works. open two Finder windows: one for the folder ~/Library/Preferences and one for /Library/Preferences.  Change the keyboard setting a couple of times to see which plist files get updated (if nothing obvious appears, check some of the subfolders in those two folders).  look for a plist file or files that seem(s) related to keyboard settings, move it/them to the desktop, and then restart the machine.  new plist files will be created with default values, and the system should reset things to the way you had it originally.  don't delete the moved plists until you're confident that nothing majorly bad got lost in the reset.  -- Ludwigs 2  18:58, 24 August 2010 (UTC)


 * I ran Software Update to make sure: 10.5.8 is current. —Tamfang (talk) 20:29, 25 August 2010 (UTC)

Wireless router.
Is there any way to increase the strength of signal from a wireless router in a favorable direction? —Preceding unsigned comment added by 113.199.199.79 (talk) 10:19, 23 August 2010 (UTC)


 * Some routers allow you to change the antenna for a directional one. But try mounting the router high on the wall (say head-height) - most have holes in the back that facilitate this. And keep it away from large metal objects like filing cabinets. -- Finlay McWalter ☻ Talk 10:46, 23 August 2010 (UTC)


 * I have never tried this myself, but googling parabolic wifi yields many do-it-yourself solutions (and some solutions you can purchase). Comet Tuttle (talk) 19:55, 23 August 2010 (UTC)


 * You can use a sector antenna for a point-to-point type link --24.85.141.156 (talk) 20:08, 25 August 2010 (UTC)

How to add a shortcut from the Programs menu in WinXP?
I have a portable program (from the excellent Nirsoft) the I have created a new folder for in the Programs folder. I also have created a shortcut for its .exe file which is currently sitting in the same folder. How do I create a shortcut from the Start/Programs menu to the .exe file? Dragging the shortcut does not work. I have done this in the past but have forgotten how to do it. Thanks 92.15.14.42 (talk) 11:15, 23 August 2010 (UTC)

I've figured out that you put the shortcut in the c:/Documents and Settings/username/Start Menu/Programs/ folder. 92.15.14.42 (talk) 12:01, 23 August 2010 (UTC)

How can I stop the sentences from appearing one on top of another when I spellcheck?
I've been trying to get an answer to this for several months, without success. For years, I've used the google spellchecker on Wikipedia. But some months ago, something changed, and both at home and at my office attempts to use the google spellchecker result in the lines of text being one on top of another, so that they are unreadable. Help? Rick Norwood (talk) 12:22, 23 August 2010 (UTC)
 * Is this using the same browser as before? --Phil Holmes (talk) 15:29, 23 August 2010 (UTC)

Yes, same browser, same everything as far as I can tell. And it happens on two different computers, using different versions of Windows. I just tried it on this page, and the same thing happened. Can you use the google spellchecker on Wikipedia? Rick Norwood (talk) 12:35, 24 August 2010 (UTC)

Amplifying brightness of LCD monitor beyond scale
Hello, I understand that the brightness of the screen is dependent on the light source behind the LCD. Do you know of a way that I can increase the brightness of my monitor (the light source) beyond the scale provided by my computer? Either by external method or program. I know that very high brightness will not be comfortable on the eyes but still...any idea of way to do it? Thanks! 109.253.213.175 (talk) 12:29, 23 August 2010 (UTC) —Preceding unsigned comment added by 109.253.213.175 (talk) 12:28, 23 August 2010 (UTC)
 * The easiest, cheapest and most reliable way is to buy a brighter screen. If you start taking one you have apart it will end up not working or if it does will have ununiform brightness - spots and stripes, along with dead areas. As a side comment, use your existing monitor in a darkened room (and take your sun glasses off). -- SGBailey (talk) 13:14, 23 August 2010 (UTC)


 * Also... if you smoke, clean the screen. I have "repaired" a few smoker's monitors with nothing more than a damp cloth. --  k a i n a w &trade; 13:52, 23 August 2010 (UTC)

שׁAh, thank you, I'll consider smoking for the last advice to work :) So just to be sure I understand, the maximum brightness of my computer's scale is the maximum available of the light source? perhaps the lights source's brightness is not fully used? there is no manual (program) to adjust the brightness more? 109.253.189.215 (talk) 06:04, 24 August 2010 (UTC)


 * Assuming your screen is clean and you have adjusted the brightness as high as it will go, the easiest way is to buy a new, brighter screen. I know of no software to directly manipulate the brightness of the monitor backlight beyond the controls already provided by the driver or the controls on the monitor itself. You might be able to get a professional (and presumably very expensive) repair to replace the backlight, though I have no idea where you might look for someone able to do that for you. You could try asking the monitor manufacturer - get contact dcetails from their website.  If you were to attempt the repair yourself, you might be able to replace the backlight but monitors are fragile and you are much more likely to break your monitor.
 * On the other hand, it did occur to me that perhaps you have some visual impairment. Windows (and probably Mac as well) have a whole lot of accessibility options which will adjust the colour scheme to increase the contrast of the various display elements. Astronaut (talk) 09:37, 24 August 2010 (UTC)

Thank you for your detailed reply! —Preceding unsigned comment added by 95.35.163.19 (talk) 12:14, 24 August 2010 (UTC)


 * Many LCD monitors have a "temperature" setting. If you can increase temperature, it will usually increase brightness and decrease contrast.  In my opinion, running with high temperature makes everything look washed out. --  k a i n a w &trade; 12:21, 24 August 2010 (UTC)

BBC IPLAYER LIVE
I lived in UK, someone sent me a url of bbciplayer live stream, and I watched it, but I don't have a tv license. Is this illegal? —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 15:43, 23 August 2010 (UTC)
 * No that's quite legal. You only need a TV licence if you're watching something that is being broadcast live at the exact same time (simulcast). You can get confirmation of this on the BBC site here.  ZX81    talk  15:52, 23 August 2010 (UTC)
 * But it WAS live, it was the live stream from the iplayer showing exactly what you'd see if you watched it on an actual television. Here's the link http://www.bbc.co.uk/iplayer/playlive/bbc_one_london/ —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 18:45, 23 August 2010 (UTC)
 * Then yes, you've answered your own question, you should have a TV licence.  ZX81    talk  21:55, 23 August 2010 (UTC)
 * Wait don't brush it off so quickly. I have not answer my own question, that's why I'm asking. So just because I visited that url and don't have a license they can prosecute me and fine me £1000?!? Surely it can't be like that, that's insane —Preceding unsigned comment added by Prize Winning Tomato (talk • contribs) 21:59, 23 August 2010 (UTC)
 * Sorry, I should have read your original message better where you did actually say it was live, but yes, theoretically they could fine you. However unless you were actually logged into to a BBC account which gave them your full name they'd only have your IP address and no way to work out who you are without having to go through the legal channels to get the information from your ISP and until they have that information they wouldn't even know if you had a tv licence or not. Likewise with the BBC login, if you had an account filled in with them with name/address then it's possible they might cross reference it with the database, I personally don't know. P.S. At the bottom of that page you linked, it does actually say: "Don't forget, to watch TV online as it's being broadcast, you still need a TV licence." Sorry I'm not able to give you a better answer.  ZX81    talk  22:09, 23 August 2010 (UTC)
 * Here is the official BBC iPlayer FAQ entry on this . Equisetum (talk &#124; email &#124; contributions) 11:09, 24 August 2010 (UTC)

Custom JPEG Quantization matrix
Do most standard JPEG decoders allow the image-file to specify a custom quantization matrix? Does the JFIF file format even have a place to store a custom quantization matrix? Or is there one specific table of default coefficients specified by the JPEG standard? Our article lists a "typical" quantization matrix" but I can find no evidence that a custom matrix is permitted to be specified in any standard location in a JFIF file. Nimur (talk) 17:29, 23 August 2010 (UTC)
 * (Followup) These guys say the <tt>DQT</tt> keyword appears in the JFIF file and there is a standard format to define quantization tables; also that multiple tables may be defined for different scans of the same image. I'm curious if many standard image softwares actually support that.  Nimur (talk) 17:46, 23 August 2010 (UTC)
 * Okay. To answer my own question: dqt is a symbol in the JPEG code stream - it is specified by the JPEG codec, published as ITU T.81 and not by the JFIF file format.  Nimur (talk) 17:57, 23 August 2010 (UTC)
 * I used to be interested in JPEG optimisers in the past and from memory quite a few of them would try to generate an optimised qtables. I also came across  some specialised usage of custom qtables. See also my post below Nil Einne (talk) 01:51, 24 August 2010 (UTC)
 * The "quality level" that you choose when saving a .jpg image chooses the quantization matrix (and also, in some applications, chroma subsampling factors). The "quality level" is not stored in the file, only the matrix is. So any decoder that can handle ordinary .jpg images of the sort that you find on the web does support custom quantization matrices. I think there are some specialized embedded decoders that don't. -- BenRG (talk) 22:28, 23 August 2010 (UTC)
 * This has some interesting discussion of qtables Nil Einne (talk) 01:51, 24 August 2010 (UTC)
 * Thanks for the feedback guys. I was particularly interested in generating my own optimized quant table: in hardware, if every element of the quant matrix is a power of two, then the entire quantization stage can be performed with a bit-select operation (the RTL equivalent of using a right shift to perform division).  This trade-off speeds compression time, at the possible expense of lower quality and/or larger file-size.  Since it looks like any QT can be specified, this seems to be a legitimate optimization.  I'm curious if it's been done before.  Nimur (talk) 07:42, 24 August 2010 (UTC)

Wii SD card trouble
I'm having a bit of a problem with my save data New Super Mario Bros. Wii. I moved my data for the game onto an SD card and then I took the card out of the console. Then I went to the game's menu to see if the data was still there and the game gave me a message telling me it had created a new save file on the Wii's memory. So I put the SD card back in the console and attempted to move the data from the SD back onto the Wii's memory but the system wouldn't let me because a "save file for New Super Mario Bros. Wii already exists on the Wii. I think I can delete the Wii save file for the game and then copy the SD card file over but I wanted to make sure that was the right thing to do before I deleted anything.--ChromeWire (talk) 18:59, 23 August 2010 (UTC)
 * Sounds right to me. The data on your Wii has just been created (I'm assuming you've not made any significant in-game progress on this new save file), so it can be safely deleted. The stuff on your SD card is what you want, so yes, copy it over and steamroller anything in the way. Vimescarrot (talk) 23:30, 23 August 2010 (UTC)
 * Sounds right to me, too. If you wanted to play it safe, you could always connect the SD card to your computer through a card reader and back up both saves. &mdash; W aterfox  ( talk ) 14:19, 24 August 2010 (UTC)

Thanks. It worked.--ChromeWire (talk) 00:10, 26 August 2010 (UTC)

Using public computers
Apart from using key loggers how could someone get your passwords when you log in say to wikipedia on a public machine? Are the passwords stored locally on the PC and if so would something like ccleaner erase them? Mo ainm ~Talk  19:50, 23 August 2010 (UTC)
 * The actual password isn't stored locally (unless the browser has a remember passwords feature enabled). Wikipedia knows you're logged in by a cookie. Unless you're using the https wikipedia server, someone might be able to monitor everything flowing over the internet connection and extract the password when you enter it to log in and click submit. 82.44.54.25 (talk) 19:53, 23 August 2010 (UTC)
 * So unless they are sniffing the network their is no way for them to get your password if you haven't allowed the browser to store your password. Mo ainm  ~Talk  19:57, 23 August 2010 (UTC)


 * If you let it do so, passwords are stored in the browser's store. There they're superficially obfuscated, but the browser needs to have them in the clear eventually so it can send them to a site. CCleaner should remove them, as should a browser's clear-private-data option, but if the machine is compromised or dishonestly operated, you can't trust them either.  And attackers don't need your password to do you serious damage - they can do that with just your session: that is, if you don't logout explicitly, and remain sporadically active, many sites will keep you logged in.   And if the session you leave open is your email, a clever attacker can ask other sites (social networking, shopping) to send one of those "I've lost my password" things. With that, they can control (and lock you out of) all those other accounts. And all with no privileged access on the machine, keyloggers, or any skillz at all.   Typing a password for anything but the most trivial things into a computer you don't trust is a risky business.  -- Finlay McWalter ☻ Talk 20:01, 23 August 2010 (UTC)


 * It's also a very good reason to use a different password for each thing. Using the same password for something trivial (like the high-score on some flash game) and something really important (like your banking) risks the trivial thing being compromised, leading to incursion into the important think. -- Finlay McWalter ☻ Talk 20:03, 23 August 2010 (UTC)


 * Public computers are largely insecure. Someone intent on getting your password can use a packet sniffer on the local network, add a keylogger, or if s/he has hacked into the machine itself can examine logs, cache files, cookies, temporary files, or other background documents (many of which are written by applications or services as part of their normal operations) which may contains records of sensitive information.  sometimes inept or overworked system administrators help them out by configuring daemons that watch internet traffic for policy violations (e.g., adding a net-nanny type software); hackers who gain access to the machine then have a wealth of added information about what gets done with the machines.  The saving grace, however, is that hackers are usually disinterested in public access machines - people who hang out in coffee shops and public libraries are not generally profitable targets.  You'd be more likely to run into a script kiddie out for yucks than a serious net prowler.  -- Ludwigs 2  20:13, 23 August 2010 (UTC)


 * (ec) If you're concerned about hard-core attacks of this sort, another danger is that the OS might choose the moment of your hitting the "Enter" key to write a bunch of memory, coincidentally including your password, out to its swap file, and the FBI analyst who swoops down on your machine right after you log in would grab that swap file and see your password. If memory serves, the TrueCrypt guys have complained for some time about not being able to properly ensure security with respect to this sort of attack, because of the behavior of the behavior of Windows with its swap file.  Comet Tuttle (talk) 20:13, 23 August 2010 (UTC)
 * There's a way to protect against the swap file issues in Windows. Professional additions have a swap wipe option on shutdown. The temp files are probably a bigger issue. I'm curious if Comet has a link to a discussion of the truecrypt guys complaining about this. Shadowjams (talk) 08:31, 26 August 2010 (UTC)
 * They could use a cold boot attack, a Man-in-the-middle attack, or sniffer to see the password as it is being sent....though I haven't seen anyone's Wikipedia account compromised from that.Smallman12q (talk) 20:34, 23 August 2010 (UTC)


 * There is also the very easy non-technical "look over your shoulder" attack. -- k a i n a w &trade; 14:06, 24 August 2010 (UTC)

Pay Pal asking for my details
When I try to log onto my Pay Pal account,  It says.... "We are currently performing regular maintenance of our security measures. Your account has been randomly selected for this maintenance, and you will now be taken through a series of identity verification pages." It then asks me to enter my card and bank details. Is this legit?? It really looks like the PayPal site and it has part of my numbers correct. ie: XXXX XXXX XXXX 1034 Am I being paranoid? —Preceding unsigned comment added by Popcorn II (talk • contribs) 20:37, 23 August 2010 (UTC)
 * Try using a different computer (maybe at a friend's house) and see if you get the same message. It sure sounds suspicious. If it only appears on one computer, it is likely that it has been infected with malware - in this case, a phishing trojan. -- 78.43.71.155 (talk) 20:55, 23 August 2010 (UTC)
 * (ec):You are not being paranoid, this is an attempt at phishing. See this example from Snopes. Looks familiar? Also see Paypal's own page on fraud prevention. You say it happens when you try to log onto your Pay Pal account. Do you actually type the address in the address bar, or do you follow a link (from an email?). If it happens when you type the address in the address bar, I would suspect that your browser has somehow been hijacked, and that you need to really purge your system of malware (=reinstall). --NorwegianBluetalk 21:00, 23 August 2010 (UTC)
 * Hmmm, I'm gonna try it on another computer. It looks loads more legit than that Snopes link. Like I say, it has some of my card details right and the url in the browser reads 'paypal.com' and it has the padlock logo. But I'm still gonna be cautious, it's not worth it for a printer cartridge!!Popcorn II (talk) 21:15, 23 August 2010 (UTC)
 * You didn't tell us how you reached the Pay Pal site. Did you type the address yourself, or did you follow a link (maybe even a link stored in your browsing history). Also remember, that if that link originated from a spam email you once opened, the amount of emails a spammer sends is enormous. Even if the ending digits are chosen at random, they will get the digits right for quite a lot of people. --NorwegianBluetalk 21:26, 23 August 2010 (UTC)
 * A link from another site is also risky (depends somewhat on the site of course). From what I can tell, PayPal does sometimes actually ask you to do that (usually if someone has tried use your account from a funny IP address) so it's possible it's legitimate. Note that if you did enter the address yourself and you are getting a scam site, ignoring it isn't helping matters. Your security is at serious risk and as NB has said you need to purge your computer of malware. Nil Einne (talk) 01:11, 24 August 2010 (UTC)

cam4
how do i change my section on cam4. how do i get into the couple section? i am a couple now. —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 20:40, 23 August 2010 (UTC)
 * Your name is Legion, for you are many? -- 78.43.71.155 (talk) 20:53, 23 August 2010 (UTC)
 * hurrrrr 24.9.250.122 (talk) 22:02, 23 August 2010 (UTC)


 * The only reference I see for cam4 in google is an online free live sex webcam. If that's what you're asking about, I suggest you check out their FAQ for account details.  -- Ludwigs 2  23:06, 23 August 2010 (UTC)